Quicker than lager turns to piss

Meaning

Very quick.

Origin

A recent , that is, 1980s, expression, originating in the UK. The earliest citation that I can find of it is from John Cooper Clarke's poem Beasley Street, which was included in the collection Snap, Crackle & Bop, 1980 and the line was probably coined by him:

People turn to poison
Quick as lager turns to piss
Sweethearts are physically sick
Every time they kiss
It's a sociologist's paradise
Each day repeats
Uneasy, cheasy, greasy, queasy
...beastly, Beasley Street